Oh yes, U r spot on.. I forgot to mention that the springs are identical..

The logic I followed was >>

In series,
* The compression is 10 cm
* This means each spring compresses by 5cm
* Since the springs are in series, both the springs experience the full 5 kg
force
* So, each spring compresses 1 cm for 1 kg (Spring constant=1)

In parallel,
* Now, the force is divided between the 2 springs
* So, force acting on each spring is 2.5 N
* So, in this case, the spring compresses to 2.5xSpring constant(1) = 2.5 cm

Hope I am right with my logic too.. Sorry, I should have mentioned this earlier